mimblewimble – What happens if a transaction is combined into two different transactions before being registered?

Suppose that a couple of people creates transaction A and instead of pissing it to one person, it shifts it to 2. Assume that transaction A is then combined with transaction B (creation of transaction AB) AND transaction C (creation of the transaction) AC). If a minor receives both AB and AC transactions, can they be safely combined in the blockchain, or can only one be chosen?